Object detection and avoidance for aerial vehicles

ABSTRACT

Aerial vehicles that are equipped with one or more imaging devices may detect obstacles that are small in size, or obstacles that feature colors or textures that are consistent with colors or textures of a landing area, using pairs of images captured by the imaging devices. Disparities between pixels corresponding to points of the landing area that appear within each of a pair of the images may be determined and used to generate a reconstruction of the landing area and a difference image. If either the reconstruction or the difference image indicates the presence of one or more obstacles, a landing operation at the landing area may be aborted or an alternate landing area for the aerial vehicle may be identified accordingly.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/838,250, filed Dec. 11, 2017, the contents of which are herebyincorporated by reference herein in their entirety. This applicationfurther claims the benefit of priority to U.S. Patent Application No.62/561,635, filed Sep. 21, 2017, the contents of which are herebyincorporated by reference herein in their entirety.

BACKGROUND

Unmanned aerial vehicles (or “UAV”) are modern, versatile machines thatare currently being used in an increasing number of monitoring,surveillance and delivery operations. An unmanned aerial vehicle may beconfigured to operate in two or more flight modes, including a forwardflight mode (or a substantially horizontal flight mode) in which theaerial vehicle travels from one point in space (e.g., a land-based pointor, alternatively, a sea-based or air-based point) to another point inspace by traveling over at least a portion of the surface of the Earth.An unmanned aerial vehicle may also be configured to engage in avertical flight mode in which the aerial vehicle travels in a verticalor substantially vertical direction from one altitude to anotheraltitude (e.g., upward or downward, from a first point on land, on seaor in the air to a second point in the air, or vice versa) substantiallynormal to the surface of the Earth, or hovers (e.g., maintains asubstantially constant altitude), with an insubstantial change inhorizontal or lateral position over the surface of the Earth. Anunmanned aerial vehicle may be further configured to operate in bothforward and vertical flight modes, e.g., in a hybrid mode in which aposition of the unmanned aerial vehicle changes in both horizontal andvertical directions. Forces of lift and thrust are commonly applied tounmanned aerial vehicles using one or more propellers, or devices havingblades that are mounted about a hub and joined to a shaft or othercomponent of a prime mover, which may rotate at angular velocities ofthousands of revolutions per minute during flight operations.

Unmanned aerial vehicles are frequently equipped with one or moreimaging devices such as digital cameras which may be used to aid in theguided or autonomous operation of an aerial vehicle, to determine whenthe aerial vehicle has arrived at or passed over a given location, or iswithin range of one or more structures, features, objects or humans (orother animals), to conduct surveillance or monitoring operations, or forany other purpose.

When transitioning from a horizontal flight mode to a vertical flightmode and preparing to land, e.g., to deliver or retrieve a payload, orfor any other reason, an unmanned aerial vehicle must determine whethera designated landing area for the unmanned aerial vehicle is free ofobstacles. If a landing area includes one or more obstacles, such ashumans, animals, structures or debris, an unmanned aerial vehicle thatattempts to land at the landing area risks causing injury to one or morehumans or other animals, or damage to one or more structures, as well asthe unmanned aerial vehicle itself. Where a landing area includes one ormore obstacles that are sufficiently large, or that include surfaceshaving one or more colors or textures that are distinct from colors ortextures of surfaces of the landing area, such obstacles may be readilyidentified in visual imaging data captured by the unmanned aerialvehicle. Where a landing area includes one or more obstacles that havesmall spatial extents, or that feature surfaces having colors ortextures that are similar to or consistent with colors or textures ofsurfaces of the landing area, however, such obstacles may not be readilyidentified in one or more visual imaging data captured thereby, yet maypose substantial hazards to the safe operation and the integrity of theunmanned aerial vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A through 1I are views of aspects of one system for objectdetection and avoidance in accordance with embodiments of the presentdisclosure.

FIG. 2 is a block diagram of one system for object detection andavoidance in accordance with embodiments of the present disclosure.

FIG. 3 is a flow chart of one process for object detection and avoidancein accordance with embodiments of the present disclosure.

FIG. 4 is a view of aspects of one system for object detection andavoidance in accordance with embodiments of the present disclosure.

FIG. 5 is a view of aspects of one system for object detection andavoidance in accordance with embodiments of the present disclosure.

FIG. 6 is a view of aspects of one system for object detection andavoidance in accordance with embodiments of the present disclosure.

FIGS. 7A and 7B are views of aspects of one system for object detectionand avoidance in accordance with embodiments of the present disclosure.

DETAILED DESCRIPTION

As is set forth in greater detail below, the present disclosure isdirected to unmanned aerial vehicles that are configured to autonomouslydetect and avoid obstacles (or obstructions) that are located in oraround landing areas for such vehicles. More specifically, one or moreof the systems and methods disclosed herein are directed to capturingtwo or more images of a landing area using one or more images that areprovided aboard an aerial vehicle, and analyzing such images todetermine whether the landing area is free of obstacles, or whether anattempted landing operation at the landing area should be modified oraborted. The images may be processed to determine disparities betweencorresponding regions of pixels within the images. In some embodiments,the pixel disparities may be determined according to an optical flowalgorithm, a matching algorithm, or by any other technique. In someembodiments, the pixel disparities may be determined by a coarse-to-finerefinement technique, in which the images are downsampled and initiallyprocessed at a low resolution to determine disparities betweencorresponding sets of pixels. The images are then upsampled in layers,and processed at progressively higher levels of resolution, with thepixel disparities being revised until the images are at their original,maximum levels of resolution.

The pixel disparities determined from images captured by the aerialvehicle may be used for multiple purposes, including to generate athree-dimensional reconstruction of the landing area, as well as tocalculate difference images based on the respective images. Inaccordance with some embodiments of the present disclosure, a landingarea may be determined to be free and clear of obstacles (orobstructions) if the three-dimensional reconstruction indicates that thelanding area is flat and smooth, and if the difference image isdetermined to be inconspicuous across the landing area. If thethree-dimensional reconstruction indicates that the landing area is notflat or smooth, or if the difference image indicates that one or moreobstacles (or obstructions) is present at the landing area, then anaerial vehicle may abort a landing operation, attempt to perform thelanding operation at an alternate landing area, search for an alternatelanding area based on images captured thereby, or take any otherrelevant action accordingly.

Referring to FIGS. 1A through 1I, a system 100 for object detection andavoidance in accordance with embodiments of the present disclosure isshown. As is shown in FIGS. 1A and 1B, the system 100 includes an aerialvehicle 110 approaching a destination 170 (e.g., a house or otherdwelling, an office building, or any other facility that may receivedeliveries of items) that bears a target marker 160 on a landingsurface. A plurality of obstacles (or obstructions) 175-1, 175-2, 175-3,175-4, 175-5, 175-6 are present within a vicinity of the target marker160, including a fence (or wall) 175-1, a tree (or other natural plant)175-2, one or more utility wires 175-3, a bicycle 175-4 (or otherobject), an automobile 175-5, and a plurality of utility poles 175-6.The obstacles 175-1, 175-2, 175-3, 175-4, 175-5, 175-6 may be static ordynamic in nature, e.g., fixed in their respective positions or mobile.

The aerial vehicle 110 may be any manned or unmanned aerial vehicleconfigured to operate in forward flight and/or vertical flight modes, ora hovering mode. The aerial vehicle 110 of FIGS. 1A and 1B includes apair of imaging devices (e.g., digital cameras) 140-1, 140-2 and a rangefinder 150. The imaging devices 140-1, 140-2 are aligned in a verticallydownward orientation, or in a substantially vertically downwardorientation, with respect to one or more principal axes of the aerialvehicle and configured to capture imaging data regarding one or moresurfaces or other objects that are located beneath the aerial vehicle110. The range finder 150 may be any device, e.g., an altimeter, a laserrange finder, another imaging device, a radar system, a sonic system, aGlobal Positioning System (or “GPS”) transceiver, or any other componentfor determining an altitude of the aerial vehicle 110, or a distance toone or more surfaces or other objects that are located beneath theaerial vehicle 110.

As is shown in FIG. 1B, the aerial vehicle 110 may begin to search forobstacles at the landing area when the aerial vehicle 110 reaches apredetermined altitude threshold. For example, as is shown in FIG. 1B,the aerial vehicle 110 may determine that it has reached an altitude zusing the range sensor 150 or any other device, and may compare thealtitude z to a threshold that may be defined on any basis, includingone or more attributes of the destination 170 or a mission of the aerialvehicle 110, any operational considerations of the aerial vehicle 110,or any other basis (e.g., prevailing weather conditions near thedestination 170). Upon confirming that the altitude z of the aerialvehicle 110 is within the predetermined altitude threshold, the aerialvehicle 110 may begin to search for the target marker 160 and evaluatethe landing area at the destination 170.

As is shown in FIGS. 1A and 1B, the aerial vehicle 110 may locate andrecognize the target marker 160 using any systems, methods ortechniques. For example, the aerial vehicle 110 may capture one or moreimages of surfaces within a vicinity of the destination 170, andrecognize one or more edges, contours, outlines, colors, textures,silhouettes, shapes or other characteristics of the target marker 160within one or more of such images. In some embodiments, the targetmarker 160 may take the form of a mat, a tarp, a sheet or any othercovering that may be laid upon a surface, e.g., by one or more personnelor machines at the destination 170, where a landing of the aerialvehicle 110 is desired. The target marker 160 may be formed from anymaterial that is flexible and sufficiently durable, including but notlimited to natural or synthetic fibers (e.g., woven or non-woven fibers)or other substrates, in order to provide an interface between the targetmarker 160 and a surface at the destination 170 upon which the targetmarker 160 is applied. In some other embodiments, the target marker 160may be formed from paint, ink, chalk or any other materials. The targetmarker 160 may further include one or more alphanumeric characters,symbols, bar codes (e.g., one-dimensional or two-dimensional bar codes,such as “QR” codes) or other markings or indicia that may be recognizedby one or more sensors aboard the aerial vehicle 110, including but notlimited to either or both of the imaging devices 140-1, 140-2. In stillother embodiments, the target marker 160 may be a natural or previouslyexisting object or artifact at the destination 170, e.g., a parkingspace or an identifier thereof; a utility structure such as a manholecover, a water main valve cover, or the like.

In some embodiments, the target marker 160 may be recognized based onanalyses of images captured by either or both of the imaging devices140-1, 140-2 alone. In some embodiments, the target marker 160 may beoutfitted with one or more systems or components that are configured totransmit one or more signals to the aerial vehicle 110 or receive one ormore signals from the aerial vehicle 110, which may then detect and/orrecognize the target marker 160 based on one or more of such signals.For example, the target marker 160 may be equipped with one or moreinfrared emitters or receivers, acoustic emitters or receivers,Wi-Fi-enabled devices, Bluetooth®-enabled devices, RFID-enabled devicesor the like. Signals transmitted and/or received by the target marker160 may be used by the aerial vehicle 110 to determine the position ofthe target marker 160 or, alternatively, the altitude z of the aerialvehicle 110. In some embodiments, the target marker 160 may berecognized based on analyses of images captured by either or both of theimaging devices 140-1, 140-2, along with one or more signals transmittedby the target marker 160 to the aerial vehicle 110, or received by thetarget marker 160 from the aerial vehicle 110.

The aerial vehicle 110 may define a landing area 165 upon detecting thetarget marker 160 at the destination 170. For example, as is shown inFIG. 1C, a center O of the target marker 160 may be determined from oneor more images captured by the imaging devices 140-1, 140-2, e.g., basedon one or more attributes of the imaging devices 140-1, 140-2 (e.g.,focal lengths), the altitude z, or one or more dimensions of the targetmarker 160, or on any other factor. Once the center O has beendetermined, the landing area 165 may be defined as a circle having apredetermined radius r from the center O. The predetermined radius r maybe determined based on one or more attributes of the aerial vehicle 110,e.g., a maximum width or other dimension of the aerial vehicle 110, plusone or more margins for safety and/or accuracy, or one or moreattributes of the aerial vehicle 110 or a mission being performedthereby. The predetermined radius r may have any value. In someembodiments, the predetermined radius r may be approximately threemeters (3 m). In some other embodiments, the landing area 165 may haveany shape other than that of a circle, such as a square, a rectangle, atriangle or any polygon or other shape. The landing area 165 may beassumed to be perfectly flat, and at an acceptable slope.

Alternatively, in some embodiments, the landing area 165 may be definedin any manner, and based on any identified position. For example, theaerial vehicle 110 may be configured to travel to a specific point andmay, upon determining that it has arrived at the specific point based onone or more GPS signals or in any other manner, define the landing area165 based on that specific point. For example, the aerial vehicle 110may define the landing area 165 as a circle having a predeterminedradius from that specific point, or as any other shape (e.g., a square,a rectangle, a triangle or any polygon or other shape) with respect tothat specific point.

As is shown in FIG. 1D, after the target marker 160 has been detectedand the landing area 165 has been defined, or after the landing area 165has been defined on any other basis, the aerial vehicle 110 may capturea plurality of images as the aerial vehicle 110 descends to the landingarea 165. The imaging devices 140-1, 140-2 may be aligned with fields ofview that include the target marker 160 and the landing area 165, andoverlap at least in part, and may be configured to capture images at anyframe rate, e.g., ten frames per second. Alternatively, the aerialvehicle 110 may feature a single imaging device aligned with a field ofview that includes the landing area 165, and is configured to captureimages at any frame rate, e.g., ten frames per second, as the aerialvehicle 110 descends to the landing area 165. In some embodiments, wherethe aerial vehicle 110 includes a single imaging device, the aerialvehicle 110 may make one or more lateral variations in position as theaerial vehicle 110 descends to the landing area 165.

Pairs of images captured by the imaging devices 140-1, 140-2 may beprocessed to determine any disparities between corresponding pixels thatappear within each of the images. As is shown in FIG. 1E, an image 145-1captured by the imaging device 140-1 and an image 145-2 captured by theimaging device 140-2 each include the target marker 160, the landingarea 165 and portions of the obstacles 175-3, 175-4. For example, as isshown in the images 145-1, 145-2, one or more of the utility wires 175-3pass over a portion of the landing area 165, and the bicycle 175-4 liesat a perimeter of the landing area 165.

The images 145-1, 145-2 may be processed to determine disparitiesbetween corresponding pixels that appear within each of the images145-1, 145-2. In some embodiments, an optical flow algorithm thatreceives the images 145-1, 145-2 as inputs and determines horizontaland/or vertical disparities between pixels appearing within each of theimages as outputs of the optical flow algorithm. Such outputs mayinclude a disparity image indicating disparities between pointsappearing within each of the images 145-1, 145-2 or, alternatively, adisplacement image indicating horizontal displacements (e.g., horizontaldisparities) between points appearing within each of the images 145-1,145-2 and/or a parallax image indicating vertical parallax (e.g.,vertical disparities) between points appearing within each of the images145-1, 145-2.

In other embodiments, the images 145-1, 145-2 may be processed accordingto a stereo matching algorithm. In such embodiments, the imaging devices140-1, 140-2 are preferably calibrated, and the images 145-1, 145-2 arepreferably pre-processed according to one or more rectificationprocesses, e.g., to place the images 145-1, 145-2 in a common plane, toeliminate any vertical parallax between corresponding pixels appearingwithin each of the images 145-1, 145-2. As a result, an output of thestereo matching algorithm depicts merely displacements (e.g., horizontaldisparities), between the corresponding pixels appearing within each ofthe images 145-1, 145-2.

In some embodiments, the processing of images 145-1, 145-2 to determinethe correspondences between points appearing in each of the respectiveimages 145-1, 145-2 may be performed first at a coarse level, e.g., ondownsampled versions of the images 145-1, 145-2, at a low level ofresolution, and next on progressively upsampled versions of the images145-1, 145-2, at gradient descent update steps on each of a plurality ofincreasingly higher levels of resolution, until correspondences ofpixels are determined based on each of the images 145-1, 145-2 in theiroriginal, highest levels of resolution. In some embodiments, after afirst processing at a coarse level of resolution, each of the images145-1, 145-2 may be progressively upsampled, e.g., by a factor of two orby another factor, until the images 145-1, 145-2 are processed at theiroriginal, highest levels of resolution.

Once disparities between pixels corresponding to points appearing withineach of the images 145-1, 145-2 have been determined, e.g., by anoptical flow algorithm, or a matching algorithm, the disparities may beused to construct (or reconstruct) the landing area 165 in threedimensions. For example. as is shown in FIG. 1F, each of the pointsP_(i) appearing within both of the images 145-1, 145-2 may beconstructed based on not only their respective disparities d_(i), butalso a baseline distance b between the imaging devices 140-1, 140-2 whenthe images 145-1, 145-2 were captured. A distance z_(i) between theaerial vehicle 110 and each of such points P_(i) may be determinedaccordingly. Using such distances z_(i), determined for a plurality ofpoints appearing within both of the images 145-1, 145-2, athree-dimensional surface map of the landing area 165 and itssurroundings may be constructed. As is shown in FIG. 1G, a top view anda side view of a surface map 115 of the landing area 165 are shown. Thesurface map 115 indicates disparity errors within planes of the images145-1, 145-2. The surface map 115 may then be compared to the landingarea 165, which is presumed to be flat and free of obstructions.Portions of the surface map 115 that do not include any disparity errorscorrespond to portions of the landing area 165 that are flat and free ofobstructions. Any discontinuities identified in the surface map 115 maybe indicative of one or more obstructions at the landing area 165,however. For example, as is shown in FIG. 1G, the surface map 115indicates the presence of an obstacle, viz., a height h₁₇₅₋₄ of thebicycle 175-4, in the landing area 165 based on disparities identifiedbetween the images 145-1, 145-2 according to an optical flow algorithm,a stereo matching algorithm, or on any other basis.

Additionally, disparities between the pixels appearing within the images145-1, 145-2 may also be used to calculate a difference image 125. Thedifference image 125 may be calculated by subtracting absoluteintensities of the images 145-1, 145-2, or by deriving intensitygradients for the images 145-1, 145-2 and comparing the intensitygradients to one another. For example, as is shown in FIG. 1H, after thepixel disparities have been determined, an input image (e.g., one of theimage 145-1 or the image 145-2) may be warped upon an output image(e.g., another of the image 145-1 or the image 145-2), resulting in thedifference image 125, which shows a difference in the appearance of theutility wire 175-3 from a left view and from a right view.Alternatively, each of the images 145-1, 145-2 may be respectivelywarped to a new (e.g., third) coordinate frame. The difference image 125may be used to detect obstacles having small spatial extents that maynot appear within a reconstruction of the landing area 165, such as thesurface map 115 of FIG. 1G. Optionally, prior to calculating thedifference image 125, either or both of the images 145-1, 145-2 may beprocessed to compensate for variations in brightness or other visualeffects within the respective images 145-1, 145-2. In some embodiments,a score may be calculated based on one or more aspects of the differenceimage 125, e.g., based on one or more pixels of the difference image125, or differences in intensity values between pixels of one of theimages 145-1, 145-2 and pixels of another of the images 145-1, 145-2.For example, a score indicative of a peak difference, a mean difference,a median difference, or any other measure or metric associated with thedifferences between such pixels may be calculated, and the landing area165 may be determined to have one or more obstacles or obstructionswhere the score exceeds a predetermined threshold. Any type or form ofscore representative of qualities of the difference image 125 may becalculated and compared to one or more thresholds in accordance with thepresent disclosure.

As is shown in FIG. 1I, after the surface map 115 and the differenceimage 125 have been derived from the images 145-1, 145-2, one or moreprocessors 112 operating aboard the aerial vehicle 110 may determinewhether the landing area 165 is free from obstructions, and may abortthe landing, or search for an alternate landing site. For example, wherethe surface map 115 indicates the presence of the bicycle 175-4 at thelanding area 165, or the difference image 125 indicates the presence ofthe utility wires 175-3 above the landing area 165, the aerial vehicle110 may determine that the landing area 165 is not free of obstructions.As a result, the aerial vehicle 110 may return to its origin or analternate location, or may attempt to locate a backup landing area(e.g., one or more landing areas that may be designated by a customer orother person associated with the destination 170) or search for analternate landing area, within a vicinity of the destination 170.

Thus, the systems and methods of the present disclosure are directed todetecting and avoiding objects during a landing operation of an unmannedaerial vehicle, or any other operation of the unmanned aerial vehicle,based on two or more images captured by the unmanned aerial vehicle. Theimages may be captured at the same time by different imaging devices,such as the imaging devices 140-1, 140-2 of the aerial vehicle 110 ofFIG. 1A through 1I, or at different times by a single imaging device.The images may be processed to determine disparities between pixels ofthe respective images, e.g., using an optical flow algorithm, a matchingalgorithm or another technique. Such disparities may be used to generatea three-dimensional reconstruction of an operating area (e.g., a landingarea) for the aerial vehicle, or to calculate a difference image of theoperating area. Where either the reconstruction or the difference imageindicates the presence of an obstacle, the aerial vehicle maypermanently or temporarily suspend the operation, search for anotheroperating area to complete the operation, or continue to evaluate thestatus of the operating area for a period of time.

Accordingly, the systems and methods of the present disclosure aredirected to determining whether one or more objects is located in,around or above a landing area based on pairs of images captured by anaerial vehicle. The images of such pairs may be captured simultaneouslyor nearly simultaneously by two imaging devices or, alternatively, atdifferent times by a single imaging device. Disparities between pointsappearing in each of the images may be determined, and used to bothreconstruct the landing area in three dimensions and also to generate adifference image from the images. The reconstruction of the landing areaand the difference image may indicate the presence of one or moreobstructions in, around or above the landing area. For example, thereconstruction may indicate the presence of one or more objects in,around or above a landing area, which is presumed to be flat, andacceptably sloped, even if such objects have colors or textures that aresimilar to colors or textures of surfaces of the landing area. Thedifference image may indicate the presence of one or more objects in,around or above a landing area, even where such objects have acomparatively small spatial extent.

Imaging data (e.g., visual imaging data) may be captured using one ormore imaging devices such as digital cameras. Such devices may generallyoperate by capturing light that is reflected from objects, and bysubsequently calculating or assigning one or more quantitative values toaspects of the reflected light, e.g., pixels, generating an output basedon such values, and storing such values in one or more data stores.Digital cameras may include one or more sensors having one or morefilters associated therewith, and such sensors may detect informationregarding aspects of any number of pixels of the reflected lightcorresponding to one or more base colors (e.g., red, green or blue) ofthe reflected light. Such sensors may generate data files including suchinformation, e.g., digital images, and store such data files in one ormore onboard or accessible data stores (e.g., a hard drive or other likecomponent), as well as one or more removable data stores (e.g., flashmemory devices), or displayed on one or more broadcast or closed-circuittelevision networks, or over a computer network such as the Internet.

A digital image is a collection of pixels, typically arranged in anarray, which defines an optically formed reproduction of one or moreobjects, backgrounds or other features of a scene and may be stored in adata file. In a visual image, each of the pixels represents oridentifies a color or other light condition associated with a portion ofsuch objects, backgrounds or features. For example, a black-and-whitevisual image includes a single bit for representing a light condition ofthe pixel in a binary fashion (e.g., either black or white), while agrayscale visual image may represent the light condition in multiplebits (e.g., two to eight bits for defining tones of gray in terms ofpercentages or shares of black-and-white), and a color visual image mayinclude groups of bits corresponding to each of a plurality of basecolors (e.g., red, green or blue), and the groups of bits maycollectively represent a color associated with the pixel. A depth imageis also a collection of pixels that defines an optically formedreproduction of one or more objects, backgrounds or other features of ascene, and may also be stored in a data file. Unlike the pixels of avisual image, however, each of the pixels of a depth image represents oridentifies not a light condition or color of such objects, backgroundsor features, but a distance to objects, backgrounds or features. Forexample, a pixel of a depth image may represent a distance between asensor of an imaging device that captured the depth image (e.g., a depthcamera or range sensor) and the respective object, background or featureto which the pixel corresponds.

Imaging data files that are stored in one or more data stores may beprinted onto paper, presented on one or more computer displays, orsubjected to one or more analyses, such as to identify items expressedtherein. Such data files may be stored in any number of formats,including but not limited to JPEG or JPG files, or Graphics InterchangeFormat (or “.GIF”), Bitmap (or “.BMP”), Portable Network Graphics (or“.PNG”), Tagged Image File Format (or “.TIFF”) files, Audio VideoInterleave (or “.AVI”), QuickTime (or “.MOV”), Moving Picture ExpertsGroup (or “.MPG,” “.MPEG” or “.MP4”) or Windows Media Video (or “.WMV”)files.

Reflected light may be captured or detected by an imaging device if thereflected light is within the device's field of view, which is definedas a function of a distance between a sensor and a lens within thedevice, viz., a focal length, as well as a location of the device and anangular orientation of the device's lens. Accordingly, where an objectappears within a depth of field, or a distance within the field of viewwhere the clarity and focus is sufficiently sharp, an imaging device maycapture light that is reflected off objects of any kind to asufficiently high degree of resolution using one or more sensorsthereof, and store information regarding the reflected light in one ormore data files.

Many imaging devices also include manual or automatic features formodifying their respective fields of view or orientations. For example,a digital camera may be configured in a fixed position, or with a fixedfocal length (e.g., fixed-focus lenses) or angular orientation.Alternatively, an imaging device may include one or more actuated ormotorized features for adjusting a position of the imaging device, orfor adjusting either the focal length (e.g., zooming the imaging device)or the angular orientation (e.g., the roll angle, the pitch angle or theyaw angle), by causing a change in a distance between the sensor and thelens (e.g., optical zoom lenses or digital zoom lenses), a change in alocation of the imaging device, or a change in one or more of the anglesdefining an angular orientation.

For example, an imaging device may be hard-mounted to a support ormounting that maintains the device in a fixed configuration or anglewith respect to one, two or three axes. Alternatively, however, animaging device may be provided with one or more motors and/orcontrollers for manually or automatically operating one or more of thecomponents, or for reorienting the axis or direction of the device,i.e., by panning or tilting the device. Panning an imaging device maycause a rotation within a horizontal plane or about a vertical axis(e.g., a yaw), while tilting an imaging device may cause a rotationwithin a vertical plane or about a horizontal axis (e.g., a pitch).Additionally, an imaging device may be rolled, or rotated about its axisof rotation, and within a plane that is perpendicular to the axis ofrotation and substantially parallel to a field of view of the device.

Some modern imaging devices may digitally or electronically adjust animage identified in a field of view, subject to one or more physical andoperational constraints. For example, a digital camera may virtuallystretch or condense the pixels of an image in order to focus or broadenthe field of view of the digital camera, and also translate one or moreportions of images within the field of view. Imaging devices havingoptically adjustable focal lengths or axes of orientation are commonlyreferred to as pan-tilt-zoom (or “PTZ”) imaging devices, while imagingdevices having digitally or electronically adjustable zooming ortranslating features are commonly referred to as electronic PTZ (or“ePTZ”) imaging devices.

Information and/or data regarding features or objects expressed inimaging data, including colors, textures or outlines of the features orobjects, may be extracted from the data in any number of ways. Forexample, colors of pixels, or of groups of pixels, in a digital imagemay be determined and quantified according to one or more standards,e.g., the RGB (“red-green-blue”) color model, in which the portions ofred, green or blue in a pixel are expressed in three correspondingnumbers ranging from 0 to 255 in value, or a hexadecimal model, in whicha color of a pixel is expressed in a six-character code, or #NNNNNN,where each of the characters N has a range of sixteen digits (i.e., thenumbers 0 through 9 and letters A through F). The first two charactersNN of the hexadecimal model refer to the portion of red contained in thecolor, while the second two characters NN refer to the portion of greencontained in the color, and the third two characters NN refer to theportion of blue contained in the color. For example, the colors whiteand black are expressed according to the hexadecimal model as #FFFFFFand #000000, respectively, while the color candy apple red is expressedas #31314A. Any means or model for quantifying a color or color schemawithin an image or photograph may be utilized in accordance with thepresent disclosure. Moreover, textures or features of objects expressedin a digital image may be identified using one or more computer-basedmethods, such as by identifying changes in intensities within regions orsectors of the image, or by defining areas of an image corresponding tospecific surfaces.

Furthermore, edges, contours, outlines, colors, textures, silhouettes,shapes or other characteristics of objects, or portions of objects,expressed in still or moving digital images may be identified using oneor more algorithms or machine-learning tools. The objects or portions ofobjects may be stationary or in motion, and may be identified at single,finite periods of time, or over one or more periods or durations. Suchalgorithms or tools may be directed to recognizing and markingtransitions (e.g., the edges, contours, outlines, colors, textures,silhouettes, shapes or other characteristics of objects or portionsthereof) within the digital images as closely as possible, and in amanner that minimizes noise and disruptions, and does not create falsetransitions. Some detection algorithms or techniques that may beutilized in order to recognize characteristics of objects or portionsthereof in digital images in accordance with the present disclosureinclude, but are not limited to, Canny edge detectors or algorithms;Sobel operators, algorithms or filters; Kayyali operators; Roberts edgedetection algorithms; Prewitt operators; Frei-Chen methods; or any otheralgorithms or techniques that may be known to those of ordinary skill inthe pertinent arts.

Stereo ranging (or stereo triangulation) is a process by which distancesor ranges to objects may be determined from digital images depictingsuch objects that are captured using imaging devices, such as digitalcameras, that are separated by a fixed distance, or from imagesdepicting such objects that are captured using an imaging device, suchas a digital camera, at different times. For example, by processingpairs of images of an environment that are captured by imaging devices,ranges to points expressed in both of the images (including but notlimited to points associated with specific objects) may be determined byfinding a virtual intersection of pairs of lines extending from therespective lenses or sensors of the imaging devices throughrepresentations of such points within each of the images. Alternatively,ranges to points expressed in a pair of images of an environment thatare captured by an imaging device at different times may be determinedby finding a virtual intersection of pairs of lines extending from aposition of a lens or sensor of the imaging device at times when each ofthe images was captured through representations of such points withineach of the images.

If each of the images of the environment is captured substantiallysimultaneously, or if conditions of the environment are substantiallyunchanged when each of the images is captured, a range to a single pointwithin the environment at a given time may be determined based on abaseline distance between positions of the lenses or sensors of the oneor more imaging devices that captured such images and a disparity, or adistance between corresponding representations of a single point inspace expressed within both of the images when the images aresuperimposed upon one another. Such processes may be completed for anynumber of points in three-dimensional space that are expressed in bothof the images, and a model of such points, e.g., a point cloud, a depthmap or a depth model, may be defined accordingly. The model of suchpoints may be updated as pairs of images are subsequently captured andprocessed to determine ranges to such points.

Distances (or depths or ranges) to objects that are represented in apair of stereo images captured by imaging devices (e.g., digitalcameras) having fields of view that overlap, at least partially may bedetermined according to one or more stereo ranging algorithms ortechniques. For each point of each object that appears in both of theimages, lines extending from the respective lenses, lens modules orother sensors of the respective imaging devices through representationsof the points of the objects in each of the images will virtuallyintersect at a location corresponding to the actual position of thatpoint, in three-dimensional space. Through the use of traditionalgeometric principles and properties, e.g., the properties of similartriangles, as well as known or knowable variables such as baselinedistance or separation between the imaging devices, the disparitybetween the points within the respective images and the focal lengths ofthe respective imaging devices, coordinates of the intersecting pointmay be determined accordingly.

Where a point in space appears in two images, e.g., as epipoles, a planedefined by the positions of the respective epipoles within the imagesand an actual position of the point in space is called an epipolarplane. The images may then be co-aligned based on their contents, e.g.,along lines corresponding to intersections of the epipolar plane withthe respective image planes, or their respective epipolar lines. Afterthe images have been aligned based on their contents, an actual positionof the object may be determined by triangulating lines extending fromlenses, lens modules or other sensors of an imaging device through therepresentations of the points in the respective images within theimaging plane. An intersection of such lines corresponds to the actualposition of the point, and a distance to the point may be determinedaccordingly based on this actual position. Stereo ranging algorithms andtechniques may be used to determine ranges or distances to each of thepoints that appears in both of the images, and such ranges or distancesmay be used to define a point cloud, a depth map or anotherthree-dimensional model of the environment in which the object isprovided. The depth model may be stored in a data file (e.g., a depthimage) or utilized for any purpose, including but not limited tonavigation, guidance, surveillance or collision avoidance.

Stereo ranging algorithms and techniques thus require determiningcorrespondences of the epipoles in each of the pair of images, with eachof the epipoles corresponding to a common point in three-dimensionalspace. When a plurality of correspondences of epipoles are identifiedfrom each of a pair of images of a scene, disparities for each of theconjugate pairs of epipoles may be determined, and a map of suchdisparities that mimics a three-dimensional structure of the scene maybe constructed accordingly if information regarding aspects of thescene, e.g., geometric parameters such as the baseline distance orseparation, the focal lengths of the imaging devices and others, isknown.

There are a number of computer-based stereo ranging algorithms andtechniques for determining real-world positions of points expressed inpairs of images of scenes, and for generating depth maps, point cloudsor other three-dimensional representations of such scenes based on suchpositions. Such algorithms or techniques may aid in the performance ofcalibration, correspondence and/or construction functions. For example,the Open Source Computer Vision (or “OpenCV”) library includes a numberof computer-based algorithms or other programming functions that aredirected to determining distances or ranges from pairs of images.Similarly, a number of other stereo ranging algorithms or techniquesprogrammed in the MATLAB language are publicly available. Computer-basedalgorithms or techniques are available from a number of other sources,as well.

Imaging devices may be integrated into surfaces of aerial vehicles andaligned horizontally or vertically, e.g., in forward or aftorientations, or in upward or downward orientations, or at any otherorientations or angles, which may be relative or absolute. In someembodiments, two or more digital cameras may be integrated into frames,control surfaces, propulsion motors, propellers or any other aspects ofan aerial vehicle. The digital cameras may be homogenous (e.g.,functionally equivalent or having the same capacities) or,alternatively, heterogeneous (e.g., having different capacities), andstereo images captured by such cameras for determining depths may beprocessed in multiple calculations. In some embodiments, an aerialvehicle may include one or more imaging devices that are integrated intofixed or moving features of the aerial vehicle. Images captured by eachof the imaging devices may be used for stereo ranging purposes, e.g., bydetermining baseline distances or separations between such imagingdevices, disparities of objects within such images, and focal lengths ofthe respective imaging devices.

Referring to FIG. 2, a block diagram of one system 200 for objectdetection and avoidance in accordance with embodiments of the presentdisclosure is shown. The system 200 of FIG. 2 includes an aerial vehicle210 and a data processing system 280 connected to one another over anetwork 290, which may include the Internet, in whole or in part. Exceptwhere otherwise noted, reference numerals preceded by the number “2”shown in FIG. 2 indicate components or features that are similar tocomponents or features having reference numerals preceded by the number“1” shown in FIGS. 1A through 1I.

The aerial vehicle 210 includes a processor 212, a memory 214 and atransceiver 216. The aerial vehicle 210 further includes a controlsystem 220, a plurality of propulsion motors 230-1, 230-2 . . . 230-n,imaging devices 240-1, 240-2 and a range finder 250.

The processor 212 may be configured to perform any type or form ofcomputing function, including but not limited to the execution of one ormore machine learning algorithms or techniques. For example, theprocessor 212 may control any aspects of the operation of the aerialvehicle 210 and the one or more computer-based components thereon,including but not limited to the propulsion motors 230-1, 230-2 . . .230-n, the imaging devices 240-1, 240-2 or the range finder 250. Forexample, the processor 212 may control the operation of one or morecontrol systems or modules, such as the control system 220, forgenerating instructions for conducting operations of one or more of thepropulsion motors 230-1, 230-2 . . . 230-n, the imaging devices 240-1,240-2 or the range finder 250, either independently or in concert withone another. Such control systems or modules may be associated with oneor more other computing devices or machines, and may communicate withthe data processing system 280 or one or more other computer devices(not shown) over the network 290, through the sending and receiving ofdigital data.

The processor 212 may be a uniprocessor system including one processor,or a multiprocessor system including several processors (e.g., two,four, eight, or another suitable number), and may be capable ofexecuting instructions. For example, in some embodiments, the processor212 may be a general-purpose or embedded processor implementing any of anumber of instruction set architectures (ISAs), such as the x86,PowerPC, SPARC, or MIPS ISAs, or any other suitable ISA. Where theprocessor 212 is a multiprocessor system, each of the processors withinthe multiprocessor system may operate the same ISA, or different ISAs.

Additionally, the aerial vehicle 210 further includes one or more memoryor storage components 214 (such as databases or data stores) for storingany type of information or data, e.g., instructions for operating theaerial vehicle 210, or information or data captured during operations ofthe aerial vehicle 210. The memory 214 may be configured to storeexecutable instructions, flight paths, flight control parameters and/orother data items accessible by or to the processor 212. The memory 214may be implemented using any suitable memory technology, such as staticrandom-access memory (SRAM), synchronous dynamic RAM (SDRAM),nonvolatile/Flash-type memory, or any other type of memory. In someembodiments, program instructions, flight paths, flight controlparameters and/or other data items may be received or sent via thetransceiver 216, e.g., by transmission media or signals, such aselectrical, electromagnetic, or digital signals, which may be conveyedvia a communication medium such as a wired and/or a wireless link.

The transceiver 216 may be configured to enable the aerial vehicle 210to communicate through one or more wired or wireless means, e.g., wiredtechnologies such as Universal Serial Bus (or “USB”) or fiber opticcable, or standard wireless protocols such as Bluetooth® or any WirelessFidelity (or “Wi-Fi”) protocol, such as over the network 290 ordirectly. The transceiver 216 may further include or be in communicationwith one or more input/output (or “I/O”) interfaces, network interfacesand/or input/output devices, and may be configured to allow informationor data to be exchanged between one or more of the components of theaerial vehicle 210, or to one or more other computer devices or systems(e.g., other aerial vehicles, not shown) via the network 290. Forexample, in some embodiments, the transceiver 216 may be configured tocoordinate I/O traffic between the processor 212 and one or more onboardor external computer devices or components. The transceiver 216 mayperform any necessary protocol, timing or other data transformations inorder to convert data signals from a first format suitable for use byone component into a second format suitable for use by anothercomponent. In some embodiments, the transceiver 216 may include supportfor devices attached through various types of peripheral buses, e.g.,variants of the Peripheral Component Interconnect (PCI) bus standard orthe Universal Serial Bus (USB) standard. In some other embodiments,functions of the transceiver 216 may be split into two or more separatecomponents, or integrated with the processor 212.

The control system 220 may include one or more electronic speedcontrols, power supplies, navigation systems and/or payload engagementcontrollers for controlling the operation of the aerial vehicle 210 andfor engaging with or releasing items, as desired. For example, thecontrol system 220 may be configured to cause or control the operationof one or more of the propulsion motors 230-1, 230-2 . . . 230-n, theimaging devices 240-1, 240-2 or the range finder 250. For example, thecontrol system 220 may cause one or more of the propulsion motors 230-1,230-2 . . . 230-n to rotate one or more propellers at desired speeds, inorder to guide the aerial vehicle 210 along a determined or desiredflight path. The control system 220 may also cause one or more of theimaging devices 240-1, 240-2 to capture any imaging data (e.g., still ormoving images) as well as any associated audio data and/or metadata. Thecontrol system 220 may operate the range finder 250 to determine a rangebetween the aerial vehicle 210 and one or more ground-based features(e.g., an altitude above such features), or a range between the aerialvehicle 210 and one or more airborne objects.

The control system 220 may further control any other aspects of theaerial vehicle 210, including but not limited to the operation of one ormore control surfaces (not shown) such as wings, rudders, ailerons,elevators, flaps, brakes, slats or other features within desired ranges,or the enactment with or release of one or more items by one or moreengagement systems (not shown). In some embodiments, the control system220 may be integrated with one or more of the processor 212, the memory214 and/or the transceiver 216.

The propulsion motors 230-1, 230-2 . . . 230-n may be any type or formof motor (e.g., electric, gasoline-powered or any other type of motor)capable of generating sufficient rotational speeds of one or morepropellers or other components to provide lift and/or thrust forces tothe aerial vehicle 210 and any payload engaged thereby, to aeriallytransport the engaged payload thereby. For example, one or more of thepropulsion motors 230-1, 230-2 . . . 230-n may be a brushless directcurrent (DC) motor such as an outrunner brushless motor or an inrunnerbrushless motor.

The aerial vehicle 210 may include any number of such propulsion motors230-1, 230-2 . . . 230-n of any kind. In some embodiments, the aerialvehicle 210 may include two propulsion motors 230-1, 230-2 . . . 230-n.In some other embodiments, the aerial vehicle 210 may include three,four, five, six, seven, eight or more propulsion motors 230-1, 230-2 . .. 230-n. For example, one or more of the propulsion motors 230-1, 230-2. . . 230-n may be aligned or configured to provide forces of lift tothe aerial vehicle 210, exclusively, while one or more of the propulsionmotors 230-1, 230-2 . . . 230-n may be aligned or configured to provideforces of thrust to the aerial vehicle 210, exclusively. Alternatively,one or more of the propulsion motors 230-1, 230-2 . . . 230-n may bealigned or configured to provide forces of lift and forces of thrust tothe aerial vehicle 210, as needed. Additionally, the propulsion motors230-1, 230-2 . . . 230-n may be fixed in their orientation on the aerialvehicle 210, or configured to vary their respective orientations, e.g.,a tilt-rotor aircraft. Moreover, the propulsion motors 230-1, 230-2 . .. 230-n may be aligned or configured to operate with differentcapacities or ratings, or at different speeds, or coupled to propellershaving different sizes and shapes.

Each of the propulsion motors 230-1, 230-2 . . . 230-n may be coupled toone or more propellers (or rotors or rotatable systems) having aplurality of shaped blades joined to a hub or boss. For example, each ofsuch propellers may be rotatably mounted to a mast or shaft associatedwith a respective one of the propulsion motors 230-1, 230-2 . . . 230-nand configured to generate forces of thrust when rotated within a fluid.Each of such propellers may include any number of blades, and may befixed pitch, adjustable pitch or variable pitch in nature. Moreover, oneor more of such propellers may be banded or shielded in any manner. Insome embodiments, one or more of the propellers may be configured torotate about a vertical axis, and to provide forces of thrust in avertical direction (e.g., upward) accordingly. In some otherembodiments, one or more of the propellers may be configured to rotateabout a horizontal axis, and to provide forces of thrust in a horizontaldirection (e.g., forward) accordingly. In still other embodiments, oneor more of the propellers may be configured to rotate about axes thatare neither horizontal nor vertical, and to provide forces of thrust indirections corresponding to such axes accordingly.

The imaging devices 240-1, 240-2 may be any form of optical recordingdevices that are embedded or mounted to surfaces of the aerial vehicle210, and may be used to photograph or otherwise record imaging data ofstructures, facilities, terrain or any other elements encountered duringoperation of the aerial vehicle 210, or for any other purpose. Theimaging devices 240-1, 240-2 may include one or more sensors, memory orstorage components and processors, and such sensors, memory componentsor processors may further include one or more photosensitive surfaces,filters, chips, electrodes, clocks, boards, timers or any other relevantfeatures (not shown). Such imaging devices 240-1, 240-2 may captureimaging data in the form of one or more still or moving images of anykind or form, as well as any relevant audio signals or other informationduring the operation of the aerial vehicle 210.

The imaging devices 240-1, 240-2 may communicate with the processor 212and/or the control system 220, or with one another, by way of a wired orwireless connection that may be dedicated or comprise all or part of aninternal network (not shown). Additionally, the imaging devices 240-1,240-2 may be adapted or otherwise configured to communicate with thedata processing system 280 by way of the network 290. Although the blockdiagram 200 of FIG. 2 includes two boxes corresponding to the imagingdevices 240-1, 240-2, those of ordinary skill in the pertinent arts willrecognize that any number or type of imaging devices may be providedaboard the aerial vehicle 210 in accordance with the present disclosure,including but not limited to digital cameras, depth sensors or rangecameras, infrared cameras, radiographic cameras or other opticalsensors.

In addition to the imaging devices 240-1, 240-2, the aerial vehicle 210may also include any number of other sensors, components or otherfeatures for controlling or aiding in the operation of the aerialvehicle 210, including but not limited to one or more environmental oroperational sensors for determining one or more attributes of anenvironment in which the aerial vehicle 210 is operating, or may beexpected to operate, including extrinsic information or data orintrinsic information or data. For example, the aerial vehicle 210 mayinclude one or more Global Positioning System (“GPS”) receivers orsensors, compasses, speedometers, altimeters, thermometers, barometers,hygrometers, gyroscopes, air monitoring sensors (e.g., oxygen, ozone,hydrogen, carbon monoxide or carbon dioxide sensors), ozone monitors, pHsensors, magnetic anomaly detectors, metal detectors, radiation sensors(e.g., Geiger counters, neutron detectors, alpha detectors), attitudeindicators, depth gauges, accelerometers, or sound sensors (e.g.,microphones, piezoelectric sensors, vibration sensors or othertransducers for detecting and recording acoustic energy from one or moredirections).

The data processing system 280 includes one or more physical computerservers 282 having one or more computer processors 284 and any number ofdata stores 286 (e.g., databases) associated therewith, and may beprovided for any specific or general purpose. For example, the dataprocessing system 280 of FIG. 2 may be independently provided for theexclusive purpose of receiving, analyzing or storing imaging data orother information or data received from the aerial vehicle 210 or,alternatively, provided in connection with one or more physical orvirtual services configured to receive, analyze or store such imagingdata or other information or data, as well as one or more otherfunctions. The servers 282 may be connected to or otherwise communicatewith the processors 284 and the data stores 286, which may store anytype of information or data, including but not limited to acousticsignals, information or data relating to imaging data, or information ordata regarding environmental conditions, operational characteristics, orpositions, for any purpose. The servers 282 and/or the computerprocessors 284 may also connect to or otherwise communicate with thenetwork 290, as indicated by line 218, through the sending and receivingof digital data. For example, the data processing system 280 may includeany facilities, stations or locations having the ability or capacity toreceive and store information or data, such as media files, in one ormore data stores, e.g., media files received from the aerial vehicle210, or from one another, or from one or more other external computersystems (not shown) via the network 290. In some embodiments, the dataprocessing system 280 may be provided in a physical location. In othersuch embodiments, the data processing system 280 may be provided in oneor more alternate or virtual locations, e.g., in a “cloud”-basedenvironment. In still other embodiments, the data processing system 280may be provided onboard one or more aerial vehicles, including but notlimited to the aerial vehicle 210.

The network 290 may be any wired network, wireless network, orcombination thereof, and may comprise the Internet in whole or in part.In addition, the network 290 may be a personal area network, local areanetwork, wide area network, cable network, satellite network, cellulartelephone network, or combination thereof. The network 290 may also be apublicly accessible network of linked networks, possibly operated byvarious distinct parties, such as the Internet. In some embodiments, thenetwork 290 may be a private or semi-private network, such as acorporate or university intranet. The network 290 may include one ormore wireless networks, such as a Global System for MobileCommunications (GSM) network, a Code Division Multiple Access (CDMA)network, a Long Term Evolution (LTE) network, or some other type ofwireless network. Protocols and components for communicating via theInternet or any of the other aforementioned types of communicationnetworks are well known to those skilled in the art of computercommunications and thus, need not be described in more detail herein.

The computers, servers, devices and the like described herein have thenecessary electronics, software, memory, storage, databases, firmware,logic/state machines, microprocessors, communication links, displays orother visual or audio user interfaces, printing devices, and any otherinput/output interfaces to provide any of the functions or servicesdescribed herein and/or achieve the results described herein. Also,those of ordinary skill in the pertinent art will recognize that usersof such computers, servers, devices and the like may operate a keyboard,keypad, mouse, stylus, touch screen, or other device (not shown) ormethod to interact with the computers, servers, devices and the like, orto “select” an item, link, node, hub or any other aspect of the presentdisclosure.

The aerial vehicle 210 and/or the data processing system 280 may use anyweb-enabled or Internet applications or features, or any otherclient-server applications or features including E-mail or othermessaging techniques, to connect to the network 290, or to communicatewith one another, such as through short or multimedia messaging service(SMS or MMS) text messages. For example, the aerial vehicle 210 may beadapted to transmit information or data in the form of synchronous orasynchronous messages to the data processing system 280 or to any othercomputer device (e.g., to one or more other aerial vehicles) in realtime or in near-real time, or in one or more offline processes, via thenetwork 290. Those of ordinary skill in the pertinent art wouldrecognize that the aerial vehicle 210 or the data processing system 280may operate or be operated by any of a number of computing devices thatare capable of communicating over the network, including but not limitedto set-top boxes, personal digital assistants, digital media players,web pads, laptop computers, desktop computers, electronic book readers,and the like. The protocols and components for providing communicationbetween such devices are well known to those skilled in the art ofcomputer communications and need not be described in more detail herein.

The data and/or computer executable instructions, programs, firmware,software and the like (also referred to herein as “computer executable”components) described herein may be stored on a computer-readable mediumthat is within or accessible by computers or computer components such asthe processor 212 or the processor 284, or any other computers orcontrol systems utilized by the aerial vehicle 210 or the dataprocessing system 280 (e.g., by one or more other aerial vehicles), andhaving sequences of instructions which, when executed by a processor(e.g., a central processing unit, or “CPU,” or a graphics processingunit, or “GPU”), cause the processor to perform all or a portion of thefunctions, services and/or methods described herein. Such computerexecutable instructions, programs, software, and the like may be loadedinto the memory of one or more computers using a drive mechanismassociated with the computer readable medium, such as a floppy drive,CD-ROM drive, DVD-ROM drive, network interface, or the like, or viaexternal connections.

Some embodiments of the systems and methods of the present disclosuremay also be provided as a computer-executable program product includinga non-transitory machine-readable storage medium having stored thereoninstructions (in compressed or uncompressed form) that may be used toprogram a computer (or other electronic device) to perform processes ormethods described herein. The machine-readable storage media of thepresent disclosure may include, but is not limited to, hard drives,floppy diskettes, optical disks, CD-ROMs, DVDs, ROMs, RAMs, erasableprogrammable ROMs (“EPROM”), electrically erasable programmable ROMs(“EEPROM”), flash memory, magnetic or optical cards, solid-state memorydevices, or other types of media/machine-readable medium that may besuitable for storing electronic instructions. Further, embodiments mayalso be provided as a computer executable program product that includesa transitory machine-readable signal (in compressed or uncompressedform). Examples of machine-readable signals, whether modulated using acarrier or not, may include, but are not limited to, signals that acomputer system or machine hosting or running a computer program can beconfigured to access, or including signals that may be downloadedthrough the Internet or other networks.

As is discussed above, an aerial vehicle may be configured to determinewhether a landing area is clear of obstacles using imaging data capturedby one or more imaging devices that are embedded or otherwise integratedinto one or more surfaces of the aerial vehicle. Referring to FIG. 3, aflow chart 300 of one process for object detection and avoidance inaccordance with embodiments of the present disclosure is shown.

At box 310, the unmanned aerial vehicle determines that it has reachedan altitude threshold within the vicinity of a destination during adescent. For example, the unmanned aerial vehicle may be equipped withone or more sensors, e.g., a laser range finder, configured to determinean altitude of the unmanned aerial vehicle with respect to one or moreground-based structures. Alternatively, the altitude of the unmannedaerial vehicle may be determined using one or more imaging devices,radar systems, sonic systems, Global Positioning System (or “GPS”)components, or the like. Additionally, the altitude threshold may bedefined on any basis. For example, the altitude threshold may be definedbased on one or more attributes or characteristics of a mission beingperformed by the unmanned aerial vehicle, e.g., a mass of a payload. Thealtitude threshold may also be defined based on one or more attributesor characteristics of a destination for the mission, e.g., any number ofhumans, animals, structures or plant life at the destination. Thealtitude threshold may further be defined based on one or more legal orregulatory requirements in effect at the destination, or on any otherfactor.

At box 312, the unmanned aerial vehicle locates a target marker at thedestination. For example, the target marker may be any visual fiducialmarking that is applied to a surface at the destination, and is intendedto be recognized by the unmanned aerial vehicle. The target marker mayinclude any identifying marking such as one or more alphanumericcharacters, symbols, bar codes (e.g., one-dimensional or two-dimensionalbar codes, such as “QR” codes) that may be imaged or scanned by theunmanned aerial vehicle and recognized as a desired location for landingthereon. For example, in some embodiments, the target marker may beformed from one or more layers of flexible and sufficiently durablematerials such as natural or synthetic fibers (e.g., woven or non-wovenfibers) or other substrates with one or more markings thereon. In someother embodiments, the target marker may be formed from paint, ink,chalk or any other materials applied to a landing surface.Alternatively, in some embodiments, the target marker may include one ormore sensors or other components for transmitting signals to orreceiving signals from the unmanned aerial vehicle, and the targetmarker may be located based on one or more of such signals.

At box 314, a landing area is defined at the destination based on acenter of the target marker. For example, the landing area may bedefined based on a predetermined radius extending from the center of thetarget marker. For example, a length, a width, a height or one or moreother dimensions of the target marker may be determined, e.g., by one ormore image segmentation techniques, and the center may be determinedfrom such dimensions. The predetermined radius may be selected based onone or more attributes of the unmanned aerial vehicle, or a missionbeing performed by the unmanned aerial vehicle, as well as one or moresafety factors or considerations associated with the destination for theunmanned aerial vehicle. Alternatively, the landing area may be definedbased on any dimension of the target marker, other than the center. Forexample, the landing area may be defined based on a buffer or otherpredetermined distance from a perimeter of the target marker. In someembodiments, the landing area may be defined based on any point, e.g., apredetermined set of coordinates, regardless of whether that point isassociated with a target marker.

At box 316, a pair of images captured by the unmanned aerial vehicleduring the descent are identified. For example, the images may have beencaptured at the same time by two different imaging devices providedaboard the unmanned aerial vehicle, with the imaging devices havingfields of view that overlap at least in part. Alternatively, the imagesmay have been captured at different times by a single imaging deviceprovided aboard the unmanned aerial vehicle. At box 320, pixeldisparities between the images previously captured by the unmannedaerial vehicle are determined. For example, in some embodiments, thepixel disparities may be determined using one or more optical flowalgorithms, which may determine disparities between corresponding pointsappearing within each of the images, along each of the dimensions of atwo-dimensional image (e.g., both displacements in an x-dimension andparallax in ay-dimension). In some other embodiments, the pixeldisparities may be determined using a stereo matching algorithm, whichmay determine disparities between corresponding points appearing withineach of the images along a single dimension (e.g., displacements in anx-dimension). Where pixel disparities are determined using a stereomatching algorithm, each of the images is preferably captured by one ofa pair of calibrated imaging devices and subsequently rectified, e.g.,transformed onto a common plane, prior to providing the images as inputsto a stereo matching algorithm.

Where the pixel disparities are determined using an optical flowalgorithm, the pixel disparities may be determined between each of theimages of the pair at a lowest level of resolution, e.g., by initiallydownsampling and processing the images at a low resolution to determinedisparities between corresponding sets of pixels. The images are thenprogressively upsampled in layers, and processed at progressively higherlevels of resolution with the pixel disparities being revised until theimages are at their original, maximum levels of resolution. The imagesmay be processed in any number of layers. For example, in someembodiments, the images may be processed in seven layers. Additionally,the resolution of each of the layers may be progressively increased atany rate and in any manner, e.g., by a factor of two, for each of thelayers.

After the pixel disparities have been determined at box 320, the imagesmay be processed to reconstruct the landing area in three dimensions,and also to generate a difference image from the images, for at leastportions of such images that depict the landing area. At box 330, thelanding area is reconstructed in three dimensions based on the pixeldisparities. For example, as is shown in FIG. 1F, the landing area maybe reconstructed in three-dimensional space using each of thedisparities that are associated with corresponding points (e.g., each ofthe epipoles of a conjugate pair) appearing within each of the images.The landing area may be reconstructed based on a baseline distancebetween each of the imaging devices that captured the images, e.g., bytriangulating each of the points with respect to image sensors of theimaging devices and their focal lengths.

At box 340, difference of Gaussian filtering is applied to thethree-dimensional reconstruction of the landing area. The difference ofGaussian filtering is applied to subtract low frequencies correspondingto a ground level of the unobstructed landing area, which is presumablyflat, unobstructed, and provided at an acceptable slope, from thethree-dimensional reconstruction. Alternatively, any type or form offiltering may be applied to the three-dimensional reconstruction of thelanding area determined at box 330.

At box 350, whether the filtered three-dimensional reconstructionindicates the presence of a non-standard surface within the landing areais determined. For example, if the filtered three-dimensionalreconstruction indicates that a portion of the landing area is neitherflat nor unobstructed, nor provided at an acceptable slope, the landingarea may be determined to have one or more obstacles located thereon. Ifthe filtered three-dimensional reconstruction is consistent with thepresumably flat and unobstructed landing area, however, or if any suchobstacles are sufficiently small or insignificant, then the landing areamay be determined to be free of obstacles, or to include obstacles thatare not substantial enough to preclude the aerial vehicle from landingsafely.

In parallel, at box 335, a difference image is generated based on thepair of images. For example, absolute intensities, or gradients inintensities, that are derived from one of the images may be subtractedfrom another of the images, thereby warping the images onto one another.At box 345, a difference image score is derived for pixels of thedifference image that correspond to the landing area. The differenceimage score may indicate an extent to which the pixels of the respectiveimages differ from one another within the landing area. The differenceimage score may be based on pixel values according to the RGB colormodel or any other model or standard. For example, the difference imagescore may indicate a peak difference, a mean difference, a mediandifference, or any other difference between such pixels betweenintensity values of corresponding pixels of the respective images. Thedifference image score may also indicate a number of pixels havingdifferences in intensity values above a predetermined threshold. Thedifference image score may further indicate whether such pixels definean area that is sufficiently large, thereby corresponding to an objectthat could pose a threat to the safe operation of the aerial vehicle, orwhether such pixels correspond to an object of insignificant size, or anobject that poses an insubstantial threat to the safe operation of theaerial vehicle.

At box 355, whether the difference image score exceeds an assignedthreshold is determined. The assigned threshold may be determined andassigned to a landing area and/or an aerial vehicle on any basis. Forexample, the assigned threshold may be based on a value of thedifference image score for a single pixel of the difference image, orfor one or more regions of pixels of the difference image. Additionally,the assigned threshold may correspond to one or more attributes of thelanding area, the aerial vehicle, or a mission being performed by theaerial vehicle, or any other factor. For example, an assigned thresholdmay be defined with respect to one or more dimensions or attributes ofan aerial vehicle (e.g., a size, a shape, a number of rotatingpropellers, an operating speed of the rotating propellers, or any otherrelevant attribute), a landing area or destination, a mission beingperformed by the aerial vehicle, or any other factor. If the differenceimage score exceeds the assigned threshold, then the landing area may bedetermined to have one or more obstacles thereon. If the differenceimage score does not exceed the assigned threshold, however, then thelanding area may be determined to be free from obstacles, or to includeobstacles that are not substantial enough to preclude the aerial vehiclefrom landing safely.

At box 360, whether either the filtered reconstruction of the landingarea or the difference image indicates the presence of one or moreobstacles in the landing area is determined. If the filteredreconstruction indicates that the landing area is not flat, unobstructedand at an acceptable slope, as presumed, or if the difference imageindicates that one or more obstacles lies on or over the landing area,then the process advances to box 365, where the landing operation isaborted, or the aerial vehicle attempts to identify an alternate landingarea, and the process ends. The alternate landing area may be designatedby one or more individuals associated with the destination, oridentified at the destination by the aerial vehicle, e.g., based on oneor more images captured thereby, or in any other manner. In someembodiments, an output of one or more algorithms (e.g., a differenceimage algorithm or a construction algorithm) may be a confidence levelor score indicative of a probability that the landing area includes oneor more obstacles.

Alternatively, the aerial vehicle may be programmed or otherwiseconfigured to take any number of other actions when either the filteredreconstruction of the landing area or the difference image indicates thepresence of one or more obstacles in the landing area. For example, arate of descent of the aerial vehicle may be reduced or halted, e.g., bytransitioning to a hovering mode, until the obstacles may be determinedto have been cleared from the landing area. Slowing a rate of descent orhovering may be particularly helpful where the obstacle is dynamic innature, such as a human, an animal or an object in motion. For example,where a dynamic obstacle is identified within one or more images, thedynamic obstacle may be tracked throughout the landing area until thedynamic obstacle has departed from the landing area, or no longer posesa hazard to the aerial vehicle. Additionally, any number of other pairsof images may be evaluated to confirm whether a determination that thelanding area includes one or more obstacles is accurate, or to asufficiently high degree of confidence. The aerial vehicle may alsotransmit one or more signals or messages to a ground-based or air-basedcontrol system, reporting the status of the landing area, and mayreceive one or more signals or messages from the control systemincluding one or more instructions for future operations.

If neither the filtered reconstruction nor the difference imageindicates that any obstacles are present in the landing area (e.g., onor above the landing area), then the process advances to box 370, wherewhether the unmanned aerial vehicle has landed at the defined landingarea is determined. If the unmanned aerial vehicle has landed, i.e., ifthe unmanned aerial vehicle has completed its descent, then the processends. If the unmanned aerial vehicle has not landed, then the processreturns to box 316, where a pair of images captured by the unmannedaerial vehicle during the descent is identified, and to box 320, wherepixel disparities between the previous images captured by the unmannedaerial vehicle are determined. The pair of images may include one of theimages that was included in the pair that was previously identified atbox 316, along with another image, e.g., where the images are capturedin series. Alternatively, the pair of images may include two images thatwere not included in any pair that was previously identified at box 316.

Although the flow chart 300 of FIG. 3 describes one process forgenerating a reconstruction of the landing area in three dimensions anda difference image in parallel following a determination of the pixeldisparities between the previous images, in some embodiments, thereconstruction of the landing area in three dimensions and thegeneration of a difference image may occur in series. Moreover, althoughthe flow chart 300 of FIG. 3 indicates that a landing operation may beaborted, or an alternate landing area may be identified, where eitherthe filtered reconstruction of the landing area or the difference imageindicates the presence of one or more obstacles in the landing areabased on pixel disparities identified for a single pair of images, insome embodiments, a determination to abort a landing operation or tosearch for an alternate landing area may be made based on pixeldisparities identified in multiple pairs of images, e.g., after apredetermined number of filtered reconstructions or difference imagesindicates that a landing area includes one or more obstacles orobstructions. In such embodiments, aborting a landing operation orsearching for an alternate landing area may be avoided where one or moreobstacles or obstructions is identified in a spurious or random manner,e.g., in only a single pair of images.

Moreover, the systems and methods of the present disclosure may beutilized to identify landing areas for aerial vehicles even where atarget marker is not utilized. For example, one or more of theembodiments disclosed herein may be utilized to identify a sufficientlysized landing area that is flat and free of obstacles or obstructions inan environment by comparing pairs of images captured of the environment.Areas that are sufficiently sized and flat, e.g., to accommodate anaerial vehicle, may be identified accordingly. Furthermore, one or moreof the systems and methods disclosed herein may be utilized inconnection with an operating area that is not associated with aground-based point, e.g., an airborne space defined by one or more setsof coordinates, or for operations that do not include a landingevolution. For example, where the aerial vehicle transitions from acurrent altitude to a desired altitude, without landing, one or more ofthe systems and methods of the present disclosure may determine whetherany obstructions remain between the aerial vehicle and the desiredaltitude. In some embodiments, an aerial vehicle may be equipped withone or more imaging devices that are aligned in a vertically downwardorientation, or in a substantially vertically downward orientation, withrespect to one or more principal axes of the aerial vehicle, andconfigured to capture imaging data regarding one or more surfaces orother objects that are located beneath the aerial vehicle, such as isshown in FIG. 1D. Alternatively, in some embodiments, an aerial vehiclemay be equipped with one or more imaging devices that are aligned in avertically upward orientation, or in a substantially vertically upwardorientation, with respect to one or more principal axes of the aerialvehicle, and configured to capture imaging data regarding one or moresurfaces or other objects that are located above the aerial vehicle. Insome embodiments, an aerial vehicle may be equipped with one or moreimaging devices that are aligned at any other angle with respect to theone or more principal axes of the aerial vehicle, and configured tocapture imaging data regarding one or more surfaces or other objectsthat are located along such axes.

In some embodiments, the systems and methods of the present disclosuremay determine pixel disparities from one or more pairs of imagescaptured simultaneously (e.g., synchronized images) using multipleimaging devices. Referring to FIG. 4, a view of aspects of one systemfor object detection and avoidance in accordance with embodiments of thepresent disclosure is shown. Except where otherwise noted, referencenumerals preceded by the number “4” shown in FIG. 4 indicate componentsor features that are similar to components or features having referencenumerals preceded by the number “2” shown in FIG. 2 or by the number “1”shown in FIGS. 1A through 1I.

As is shown in FIG. 4, a system 400 includes an aerial vehicle 410approaching a landing area 465. The aerial vehicle 410 is outfitted witha pair of imaging devices 440-1, 440-2 that are aligned in substantiallyvertically downward orientations with respect to principal axes (e.g.,normal axis, lateral axis, longitudinal axis) of the aerial vehicle 410,and include one or more surface features within their respective fieldsof view, which overlap at least in part. In some embodiments, thelanding area 465 may be defined upon recognizing a fiducial marking ofany type or form (e.g., the target marker 160 of FIG. 1A) on the one ormore surface features. For example, one or more points associated with afiducial marking may be detected, and boundaries of the landing area 465may be established with respect to such points, e.g., based on apredetermined radius from a given point, or based on any other boundaryprovided about the given point. In other embodiments, however, thelanding area 465 may be defined at any time or in any manner, and on anybasis. For example, the landing area 465 may be defined based on anypoint, e.g., a point defined based on one or more sets of coordinates,regardless of whether the point is associated with a target marker orany other object.

The capture of images by the imaging devices 440-1, 440-2 may beinitiated or triggered in any manner. For example, the aerial vehicle410 may determine that it is approaching a predetermined ground-basedlocation or altitude (e.g., using one or more position sensors, such asa GPS transceiver, or an altimeter or other system), and may begincapturing imaging data upon approaching the predetermined ground-basedlocation or altitude. Alternatively, the aerial vehicle 410 may beconfigured to determine when it is approaching one or more ground-basedor airborne features, e.g., structures, aircraft, animals or any otherobjects, or when one or more ground-based or airborne features areapproaching it, such as by using one or more radar systems, sonicsystems or imaging devices. The aerial vehicle 410 may thus begincapturing imaging data upon determining that the aerial vehicle 410 isapproaching such features, or upon determining that such features areapproaching the aerial vehicle 410. The aerial vehicle 410 may alsobegin to capture imaging data at a predetermined time or date.

The imaging devices 440-1, 440-2 of the aerial vehicle 410 may begin tocapture images, or may continue capturing images, as the aerial vehicle410 descends toward the landing area 465. For example, as is shown inFIG. 4, the imaging devices 440-1, 440-2 may capture pairs of images attime t₀, time t₁, time t₂, time t₃ . . . until time t_(n), when theaerial vehicle 410 has landed at the landing area 465, when the landingoperation has been aborted, or when the capture of images by the imagingdevices 440-1, 440-2 has been terminated for any reason. In someembodiments, the imaging devices 440-1, 440-2 may be configured tocapture images in series, e.g., at a predetermined or constant framerate, or at specific intervals.

Pairs of images captured by the imaging devices 440-1, 440-2 may beprocessed to recognize pixel disparities therebetween, according to anymethods or techniques. For example, an image captured by the imagingdevice 440-1 at a given time (e.g., one or more of time t₀, time t₁ timet₂, time t₃ or time t_(n)), and an image captured by the imaging device440-2 at the same time may be provided to an optical flow algorithm asinputs. The optical flow algorithm may return a field of vectorsrepresenting disparities of pixels from an image captured by the imagingdevice 440-1 at a given time and an image captured by the imaging device440-2 at the given time, or vice versa. The optical flow algorithm mayoperate in a sparse or a dense manner, based on some or all of thepixels in the images captured by the respective imaging devices 440-1,440-2. For example, in some embodiments, portions of the respectiveimages corresponding to or depicting the landing area 465 may berecognized and extracted therefrom. An optical flow algorithm mayoperate in a sparse manner, and may generate a sparse reconstruction ofthe landing area 465 based on disparities between portions of therespective images that correspond to the landing area 465.

The pixel disparities may be used to generate three-dimensionalreconstructions of the landing area 465, and to determine whether suchreconstructions are flat and smooth, or whether such reconstructionsinclude one or more obstructions that inhibit a landing operation orother evolution thereon.

Alternatively, an image captured by the imaging device 440-1 at a giventime (e.g., one or more of time t₀, time t₁, time t₂, time t₃ or anytime t₀), and an image captured by the imaging device 440-2 at the sametime or at approximately the same time may be provided to a stereomatching algorithm as inputs, and a plurality of disparities (e.g.,vectors having horizontal and/or vertical directional components)between pixels of one of the images and pixels of another of the imagesmay be returned as an output. In some embodiments, the images may berectified prior to executing the stereo matching algorithm, therebyensuring that the pixel disparities identified within such images arelimited to a single direction, e.g., horizontal or vertical, or anyother single direction.

In some embodiments, the systems and methods of the present disclosuremay determine pixel disparities from one or more pairs of imagescaptured at different times using a single imaging device. Referring toFIG. 5, a view of aspects of one system for object detection andavoidance in accordance with embodiments of the present disclosure isshown. Except where otherwise noted, reference numerals preceded by thenumber “5” shown in FIG. 5 indicate components or features that aresimilar to components or features having reference numerals preceded bythe number “4” shown in FIG. 4, by the number “2” shown in FIG. 2 or bythe number “1” shown in FIGS. 1A through 1I.

As is shown in FIG. 5, a system 500 includes an aerial vehicle 510approaching a landing area 565. The aerial vehicle 510 is outfitted withan imaging device 540 that is aligned in a substantially verticallydownward orientation with respect to principal axes (e.g., normal axis,lateral axis, longitudinal axis) of the aerial vehicle 510, and includesone or more surface features within their respective fields of view. Thelanding area 565 may be defined on any basis, e.g., based on one or morefiducial markings.

The imaging device 540 may capture images in series, e.g., in astreaming format, or at a predetermined interval. The capture of theimages by the imaging device 540 may be initiated or triggered in anymanner, at any time and on any basis. For example, the aerial vehicle510 may be configured to begin capturing images upon determining thatthe aerial vehicle 510 has arrived at a predetermined location oraltitude, upon determining that the aerial vehicle 510 has approached oris approaching a ground-based or airborne object, or at a predeterminedtime, or on any other basis.

Pairs of images captured by the imaging device 540 may be processed torecognize pixel disparities therebetween, according to any methods ortechniques. For example, an image captured by the imaging device 540 ata given time (e.g., one or more of time t₀, time t₁, time t₂, time t₃,time t₄, time t₅, time t₆, time t_(n-1) or time t_(n)), and an imagecaptured by the imaging device 540 at another time (e.g., another of thetime t₀, time t₁, time t₂, time t₃, time t₄, time t₅, time t₆, timet_(n-1) or time t_(n)) may be provided to an optical flow algorithm asinputs. The optical flow algorithm may return a field of vectorsrepresenting disparities of pixels from a first one of the images to asecond one of the images, or vice versa. The pixel disparities may beused to generate three-dimensional reconstructions of the landing area565, and to determine whether such reconstructions are flat and smooth,or whether such reconstructions include one or more obstructions thatinhibit a landing operation or other evolution thereon. Alternatively,an image captured by the imaging device 540 at a given time (e.g., oneor more of time t₀, time t₁, time t₂, time t₃, time t₄, time t₅, timet₆, time t_(n-1) or time t_(n)), and an image captured by the imagingdevice 540 at a later time may be provided to stereo matching algorithmas inputs, and a plurality of disparities (e.g., vectors havinghorizontal and/or vertical directional components) between pixels of oneof the images and pixels of another of the images may be returned as anoutput. In some embodiments, the images may be rectified prior toexecuting the stereo matching algorithm, thereby ensuring that the pixeldisparities identified within such images are limited to a singledirection, e.g., horizontal or vertical, or any other single direction.

In some embodiments, the aerial vehicle 510 may be programmed orotherwise configured to conduct one or more lateral variations inposition during operations, in order to create some form of lateralseparation between positions of the imaging device 540 at the time t₀,time t₁, time t₂, time t₃, time t₄, time t₅, time t₆, time t_(n-1) ortime t_(n). For example, during a landing operation or other operationin which the imaging device 540 is operated to capture images during adescent or hover, the aerial vehicle 510 may operate one or more controlsurfaces or stagger the operation of one or more propulsion motors, orany other aspect of the aerial vehicle 510, as desired, to cause theaerial vehicle 510 to deviate from a vertical axis. By varying theposition of the imaging device 540 with respect to the vertical axis,the aerial vehicle 510 may implement or expand a baseline distancebetween such positions, thereby enhancing a level of accuracy of pixeldisplacements determined based on images captured by the imaging device540.

Disparities between pixels may be determined by any method or techniquein accordance with the present disclosure. For example, in someembodiments, pixel disparities may be determined using one or moreoptical flow algorithms, which may determine such discrepancies.Referring to FIG. 6, a view of aspects of one system for objectdetection and avoidance in accordance with embodiments of the presentdisclosure is shown. Except where otherwise noted, reference numeralspreceded by the number “6” shown in FIG. 6 indicate components orfeatures that are similar to components or features having referencenumerals preceded by the number “5” shown in FIG. 5, by the number “4”shown in FIG. 4, by the number “2” shown in FIG. 2 or by the number “1”shown in FIGS. 1A through 1I.

As is shown in FIG. 6, the identification of a common pixel P_(n) inimages 645-1, 645-2 captured using one or more imaging devices (notshown) is represented by a pair of image pyramids. The images 645-1,645-2 may have been captured using a single imaging device at differenttimes, such as is shown in FIG. 5, or using two imaging devices, at thesame time (e.g., synchronized) or different times, such as is shown inFIG. 4. For example, at a first level of refinement, e.g., a most coarselevel of refinement, or level n, the pixel P_(n) is readily apparentwithin each of the images 645-1, 645-2, at no disparity in either ahorizontal or a vertical direction, such that D_(x)=0 and D_(y)=0.Successively, as the images 645-1, 645-2 are subjected to increasingrefinement, and the disparities between the appearance of the pixelP_(n) within the respective images 645-1, 645-2 become increasinglyclearer at subsequent levels of refinement (n−1), (n−2), and so on,until the precise disparities that D_(x), D_(y), are determined at afinal level of refinement, or level 0.

Any number of optical flow algorithms may be utilized in accordance withthe present disclosure, and such algorithms may operate in accordancewith any manner or technique. For example, in some embodiments, anoptical flow algorithm may operate according to a Lucas-Kanade method,in which a field of vectors signifying pixel disparities between a pairof images is generated. Additionally, the optical flow algorithm may besparse, such as the Lucas-Kanade method, in which a subset of the commonpixels are evaluated to identify and calculate the respectivedisparities therebetween, and an output in the form of an optical flowvector field is computed for each of the respective pixels.Alternatively, the optical flow algorithm may be dense, such that eachof the pixels of the respective images are evaluated to identify andcalculate the respective disparities therebetween. In some embodiments,where a pair of images depict all or a portion of a landing area, theportions of such images that depict the landing area may be extractedtherefrom, and subjected to a sparse optical flow algorithm in order toidentify the disparities between their respective pixels. Suchdisparities may be used to generate a three-dimensional reconstructionof the landing area, or to generate a difference image of the landingarea.

Pixel disparities may also be determined using a stereo-matchingalgorithm. Referring to FIGS. 7A and 7B, views of aspects of one systemfor object detection and avoidance in accordance with embodiments of thepresent disclosure is shown. Except where otherwise noted, referencenumerals preceded by the number “7” shown in FIG. 7A or 7B indicatecomponents or features that are similar to components or features havingreference numerals preceded by the number “6” shown in FIG. 6, by thenumber “5” shown in FIG. 5, by the number “4” shown in FIG. 4, by thenumber “2” shown in FIG. 2 or by the number “1” shown in FIGS. 1Athrough 1I.

As is shown in FIG. 7A, a system 700 includes an aerial vehicle 710approaching a landing area 765. The aerial vehicle 710 is outfitted witha pair of imaging devices 740-1, 740-2, each having fields of view FOV₁,FOV₂ that overlap at least in part and include at least a portion of thelanding area 765 and one or more other surface features therein. Theimaging devices 740-1, 740-02 are aligned in substantially verticallydownward orientations with respect to principal axes (e.g., normal axis,lateral axis, longitudinal axis) of the aerial vehicle 710. The landingarea 765 may be defined on any basis, e.g., based on one or morefiducial markings. As is shown in FIG. 7A, the landing area 765 includesa plurality of objects 775-1, 775-2, 775-3 thereon.

In accordance with the present disclosure, images 745-1, 745-2 capturedusing the respective imaging devices 740-1, 740-2 may be processed usingone or more stereo matching algorithms. As is shown in FIG. 7B, each ofthe pixels of the image 745-1 may be warped onto one of the pixels ofthe image 745-2, or vice versa, according to a deformation model, or inany other manner. Prior to warping the pixels of the respective images745-1, 745-2, the images 745-1, 745-2 may be rectified, or aligned suchthat corresponding epipolar lines are parallel to one another. Forexample, as is shown in FIG. 7B, points G₁, G₂ of the object 775-1 ineach of the images 745-1, 745-2 are aligned by rectification, anddisparities ΔG₁, ΔG₂ between pixels corresponding to such points withinthe respective images 745-1, 745-2, e.g., differences between positionsof the points G₁, G₂ of the object 775-1 in each of the images 745-1,745-2 may be determined in a horizontal direction (e.g., displacements)with respect to one another. Because the images 745-1, 745-2 arerectified, the disparities between the pixels consist of horizontaldisplacements, and do not include any vertical parallax. Similarly, asis shown in FIG. 7B, points P₁, P₂ of the object 775-2 in each of theimages 745-1, 745-2 are aligned by rectification, and disparities ΔP₁,ΔP₂ between pixels corresponding to such points within the respectiveimages 745-1, 745-2, e.g., differences between positions of the pointsP₁, P₂ of the object 775-2 in each of the images 745-1, 745-2 may bedetermined in a horizontal direction with respect to one another.Finally, as is also shown in FIG. 7B, a point B of the object 775-3 ineach of the images 745-1, 745-2 is aligned by rectification, and adisparity ΔB between pixels corresponding to such points within therespective images 745-1, 745-2, e.g., differences between positions ofthe point B of the object 775-3 in each of the images 745-1, 745-2 maybe determined in a horizontal direction with respect to one another. Asis discussed above, the use of rectified images captured by calibratedimaging devices ensures that epipolar lines between the respectivepositions G₁, G₂, P₁, P₂, B are aligned in parallel with one another,and that the disparities ΔG₁, ΔG₂, ΔP₁, ΔP₂, ΔB consist of horizontaldisplacements, and do not include any vertical parallax.

Although the disclosure has been described herein using exemplarytechniques, components, and/or processes for implementing the systemsand methods of the present disclosure, it should be understood by thoseskilled in the art that other techniques, components, and/or processesor other combinations and sequences of the techniques, components,and/or processes described herein may be used or performed that achievethe same function(s) and/or result(s) described herein and which areincluded within the scope of the present disclosure.

As used herein, the terms “forward” flight or “horizontal” flight referto flight in a direction substantially parallel to the ground (i.e., sealevel). As used herein, the term “vertical” flight refers to flight in adirection extending substantially radially outward from a center of theEarth. Those of ordinary skill in the pertinent arts will recognize thatflight trajectories may include components of both “forward” flight or“horizontal” flight and “vertical” flight vectors. As used herein, theterm “disparity” may be used to refer to differences in positions of acommon pixel or pixel in two different image frames. Thus, the term“disparity” may refer to horizontal differences in position, which aresometimes referred to as “displacements,” vertical differences inposition, which are sometimes referred to as “parallax,” or differencesin position that are both horizontal and vertical, or aligned along anyother axis, in accordance with the present disclosure. In this regard,the terms “disparity,” “displacement” or “parallax” may be usedinterchangeably to refer to differences in position of a pixel or pixelsin two or more image frames. Moreover, as used herein, the terms“obstacle” and “obstruction” may refer to any object that may bepresent, temporarily or permanently, within an operating area of anaerial vehicle. For example, an obstacle or an obstruction may be staticor dynamic, e.g., mobile, such as a human, an animal or an object suchas a bicycle, a tricycle, a stroller, a skateboard or a ball. The terms“obstacle” and “obstruction” are used interchangeably herein.

Although some of the embodiments disclosed herein reference the use ofunmanned aerial vehicles to deliver payloads from warehouses or otherlike facilities to customers, those of ordinary skill in the pertinentarts will recognize that the systems and methods disclosed herein arenot so limited, and may be utilized in connection with any type or formof aerial vehicle (e.g., manned or unmanned) having fixed or rotatingwings for any intended industrial, commercial, recreational or otheruse. Moreover, those of ordinary skill in the pertinent arts willrecognize that one or more of the embodiments disclosed herein may beutilized in connection with any operation of an aerial vehicle, and arenot limited to landing operations. For example, where an aerial vehicleis programmed or instructed to perform a surveillance operationrequiring forward or vertical flight, or hovering, in a given area, theaerial vehicle may capture images and determine disparities betweenpixels represented within such images when determining whether the givenarea is free and clear of obstructions, or whether operations within thegiven area may be safely performed as desired or intended. As isdiscussed above, where a landing area is defined in two dimensions,e.g., with respect to a two-dimensional surface, whether a landingoperation may safely occur may be determined by calculating pixeldisparities and using the pixel disparities to generate both athree-dimensional reconstruction of a landing area and a differenceimage for the landing area. In accordance with the present disclosure,an operating area may be defined either in two dimensions (e.g., aplanar region in space) or in three dimensions (e.g., a volumetricregion in space), and the operating area may but need not be associatedwith any given surface. In some embodiments, the systems and methods ofthe present disclosure may be used to determine whether atwo-dimensional region in space, or a three-dimensional region in space,includes one or more obstacles or obstructions that may preclude,inhibit or complicate the performance of one or more evolutions withinsuch regions by an aerial vehicle.

It should be understood that, unless otherwise explicitly or implicitlyindicated herein, any of the features, characteristics, alternatives ormodifications described regarding a particular embodiment herein mayalso be applied, used, or incorporated with any other embodimentdescribed herein, and that the drawings and detailed description of thepresent disclosure are intended to cover all modifications, equivalentsand alternatives to the various embodiments as defined by the appendedclaims. Moreover, with respect to the one or more methods or processesof the present disclosure described herein, including but not limited tothe processes represented in the flow chart of FIG. 3, orders in whichsuch methods or processes are presented are not intended to be construedas any limitation on the claimed inventions, and any number of themethod or process steps or boxes described herein can be combined in anyorder and/or in parallel to implement the methods or processes describedherein. Also, the drawings herein are not drawn to scale.

Conditional language, such as, among others, “can,” “could,” “might,” or“may,” unless specifically stated otherwise, or otherwise understoodwithin the context as used, is generally intended to convey in apermissive manner that certain embodiments could include, or have thepotential to include, but do not mandate or require, certain features,elements and/or steps. In a similar manner, terms such as “include,”“including” and “includes” are generally intended to mean “including,but not limited to.” Thus, such conditional language is not generallyintended to imply that features, elements and/or steps are in any wayrequired for one or more embodiments or that one or more embodimentsnecessarily include logic for deciding, with or without user input orprompting, whether these features, elements and/or steps are included orare to be performed in any particular embodiment.

Disjunctive language such as the phrase “at least one of X, Y, or Z,” or“at least one of X, Y and Z,” unless specifically stated otherwise, isotherwise understood with the context as used in general to present thatan item, term, etc., may be either X, Y, or Z, or any combinationthereof (e.g., X, Y, and/or Z). Thus, such disjunctive language is notgenerally intended to, and should not, imply that certain embodimentsrequire at least one of X, at least one of Y, or at least one of Z toeach be present.

Unless otherwise explicitly stated, articles such as “a” or “an” shouldgenerally be interpreted to include one or more described items.Accordingly, phrases such as “a device configured to” are intended toinclude one or more recited devices. Such one or more recited devicescan also be collectively configured to carry out the stated recitations.For example, “a processor configured to carry out recitations A, B andC” can include a first processor configured to carry out recitation Aworking in conjunction with a second processor configured to carry outrecitations B and C.

Language of degree used herein, such as the terms “about,”“approximately,” “generally,” “nearly” or “substantially” as usedherein, represent a value, amount, or characteristic close to the statedvalue, amount, or characteristic that still performs a desired functionor achieves a desired result. For example, the terms “about,”“approximately,” “generally,” “nearly” or “substantially” may refer toan amount that is within less than 10% of, within less than 5% of,within less than 1% of, within less than 0.1% of, and within less than0.01% of the stated amount.

Although the invention has been described and illustrated with respectto illustrative embodiments thereof, the foregoing and various otheradditions and omissions may be made therein and thereto withoutdeparting from the spirit and scope of the present disclosure.

What is claimed is:
 1. A method for operating an unmanned aerialvehicle, the method comprising: locating, by at least one imaging deviceprovided on the unmanned aerial vehicle, a target marker on a surfacebeneath the unmanned aerial vehicle; defining a landing area based atleast in part on at least a portion of the target marker, wherein thelanding area comprises a geometric shape defined with respect to theportion of the target marker; causing the unmanned aerial vehicle todescend toward the surface beneath the unmanned aerial vehicle;capturing, by the at least one imaging device, a first image includingat least a portion of the surface beneath the unmanned aerial vehicle,wherein the first image is captured while the unmanned aerial vehicle isdescending toward the surface beneath the unmanned aerial vehicle;capturing, by the at least one imaging device, a second image includingat least a portion of the surface beneath the unmanned aerial vehicle,wherein the second image is captured while the unmanned aerial vehicleis descending toward the surface beneath the unmanned aerial vehicle;determining disparities between pixels corresponding to at least aplurality of points depicted in the first image and pixels correspondingto at least the plurality of points depicted in the second image;generating a reconstruction of at least the landing area based at leastin part on the disparities; detecting at least one airborne obstructionabove at least a portion of the landing area based at least in part onthe reconstruction; and in response to detecting the at least oneairborne obstruction, causing the aerial vehicle to stop descendingtoward the surface beneath the unmanned aerial vehicle.
 2. The method ofclaim 1, wherein the at least one airborne obstruction comprises atleast one of a wire or a clothesline.
 3. The method of claim 1, whereinthe at least one imaging device comprises a first imaging device and asecond imaging device, wherein the first imaging device and the secondimaging device are separated by a baseline distance, wherein the firstimage is captured by the first imaging device, wherein the second imageis captured by the second imaging device, and wherein generating thereconstruction of the landing area comprises: calculating, for each ofthe plurality of points, a distance between one of the pixelscorresponding to the plurality of points depicted in the first image toone of the pixels corresponding to the plurality of points depicted inthe second image, wherein the disparities are determined based at leastin part on the distances calculated for each of the plurality of points.4. The method of claim 1, wherein determining the disparities comprises:providing each of the first image and the second image to an opticalflow algorithm as inputs; and receiving an output from the optical flowalgorithm, wherein the output comprises a vector field comprising aplurality of vectors, and wherein each of the vectors represents adisparity between one of the pixels corresponding to the plurality ofpoints depicted in the first image and one of the pixels correspondingto the plurality of points depicted in the second image.
 5. The methodof claim 1, wherein determining the disparities comprises: matching eachof the pixels corresponding to the plurality of points depicted in thefirst image to one of the pixels corresponding to the plurality ofpoints depicted in the second image; and determining, for each of thepixels corresponding to the plurality of points depicted in the firstimage, a distance to the matched one of the pixels corresponding to theplurality of points depicted in the second image, wherein each of thedistances calculated for each of the plurality of points is one of thedisparities.
 6. A method comprising: capturing a first image by at leastone imaging device provided aboard an aerial vehicle, wherein a field ofview of the at least one imaging device includes at least one surface ata first location; capturing a second image by the at least one imagingdevice; defining a first operating area for performance of an evolutionby the aerial vehicle with respect to the at least one surface based atleast in part on at least one of the first image or the second image;determining a first plurality of pixel disparities between a firstplurality of pixels of the first image and a second plurality of pixelsof the second image, wherein at least some of the first plurality ofpixels of the first image correspond to points of the first operatingarea depicted within the first image, and wherein at least some of thesecond plurality of pixels correspond to the points of the firstoperating area depicted within the second image; determining whether thefirst operating area includes at least one obstruction based at least inpart on the first plurality of pixel disparities; and in response todetermining that the first operating area includes the at least oneobstruction, suspending the evolution of the aerial vehicle.
 7. Themethod of claim 6, further comprising: in response to determining thatthe first operating area does not include the at least one obstruction,performing the evolution of the aerial vehicle at the first operatingarea.
 8. The method of claim 6, wherein determining the first pluralityof pixel disparities comprises: providing each of the first image andthe second image to an optical flow algorithm as inputs; and receivingan output from the optical flow algorithm, wherein the output comprisesa vector field comprising a plurality of vectors, and wherein each ofthe plurality of vectors represents one of the pixel disparities.
 9. Themethod of claim 6, wherein determining the first plurality of pixeldisparities comprises: matching each of the first plurality of pixels ofthe first image to one of the second plurality of pixels of the secondimage; and determining, for each of the first plurality of pixels, adistance to the matched one of the second plurality of pixels of thesecond image, wherein each of the distances corresponds to one of thepixel disparities.
 10. The method of claim 6, wherein the at least oneimaging device comprises a first imaging device and a second imagingdevice, wherein the first imaging device and the second imaging deviceare separated by a baseline distance, wherein the first image iscaptured by the first imaging device, wherein the second image iscaptured by the second imaging device, and wherein determining whetherthe first operating area includes at least one obstruction based atleast in part on the first plurality of pixel disparities comprises:calculating distances to each of the points of the first operating areabased at least in part on the first plurality of pixel disparities; andgenerating a first three-dimensional reconstruction of the firstoperating area based at least in part on the distances, wherein whetherthe first operating area includes the at least one obstruction isdetermined based at least in part on the first three-dimensionalreconstruction of the first operating area.
 11. The method of claim 10,further comprising: performing a difference of Gaussian filter on thefirst three-dimensional reconstruction, wherein determining whether thefirst operating area includes the at least one obstruction comprises:determining whether the first operating area includes at least oneobstruction based at least in part on at least the filtered firstthree-dimensional reconstruction.
 12. The method of claim 6, wherein theat least one imaging device comprises a first imaging device, whereinthe first image is captured by the first imaging device at a first time,wherein the second image is captured by the first imaging device at asecond time.
 13. The method of claim 6, wherein the first image iscaptured at a first time and the second image is captured atapproximately the first time, and wherein the method further comprises:in response to determining that the first operating area includes the atleast one obstruction, capturing a third image by the at least oneimaging device during the performance of the evolution by the aerialvehicle, wherein the third image is captured at a second time; capturinga fourth image by the at least one imaging device during the performanceof the evolution by the aerial vehicle, wherein the fourth image iscaptured at approximately the second time; defining a second operatingarea for the performance of the evolution with respect to the at leastone surface based at least in part on at least one of the third image orthe fourth image; determining a second plurality of pixel disparitiesbetween a third plurality of pixels of the third image and a fourthplurality of pixels of the fourth image, wherein at least some of thethird plurality of pixels of the third image correspond to points of thesecond operating area depicted within the third image, and wherein atleast some of the fourth plurality of pixels corresponds to the pointsof the second operating area depicted within the fourth image;determining whether the second operating area includes at least oneobstruction based at least in part on at least the second plurality ofpixel disparities; and in response to determining that the secondoperating area does not include the at least one obstruction, performingthe evolution of the aerial vehicle in the second operating area. 14.The method of claim 6, wherein defining the first operating area for theperformance of the evolution by the aerial vehicle with respect to theat least one surface comprises: detecting at least one fiducial markeron the at least one surface within the at least one of the first imageor the second image; recognizing at least one attribute of the at leastone fiducial marker; and selecting at least one point associated withthe at least one fiducial marker based at least in part on the at leastone attribute, wherein the first operating area is a circle having apredetermined radius from the at least one point.
 15. The method ofclaim 6, wherein determining whether the first operating area includesthe at least one obstruction based at least in part on the firstplurality of pixel disparities comprises: determining, for each of thefirst plurality of pixels of the first image, a difference between anintensity value of one of the first plurality of pixels of the firstimage and an intensity value of a corresponding one of the secondplurality of pixels of the second image; generating a difference imagebased at least in part on the differences between the intensity values;calculating a score for the difference image, wherein the scorecomprises at least one of a peak difference, a mean difference or amedian difference in the intensity values between the one of the firstplurality of pixels of the first image and the corresponding one of thesecond plurality of pixels of the second image; and determining that thescore exceeds a predetermined threshold, wherein the evolution of theaerial vehicle is suspended in response to determining that the scoreexceeds the predetermined threshold.
 16. The method of claim 6, whereinthe at least one obstruction comprises at least one wire or at least oneclothesline, and wherein the at least one wire or the at least oneclothesline is suspended over or within a vicinity of at least a portionof the first operating area.
 17. The method of claim 6, furthercomprising: receiving, by at least one transceiver associated with theaerial vehicle, information regarding a destination for the performanceof the evolution by the aerial vehicle, wherein the informationregarding the destination comprises an identifier of at least one pointat the destination, and wherein the evolution comprises at least one ofa landing, a delivery of at least a first item or a retrieval of atleast a second item; and determining, by at least one sensor associatedwith the aerial vehicle, that the aerial vehicle is within a vicinity ofthe at least one point, wherein the first image and the second image arecaptured in response to determining that the aerial vehicle is withinthe vicinity of the at least one point.
 18. A method comprising:capturing a first image by a first imaging device aboard an unmannedaerial vehicle at a first time; capturing a second image by a secondimaging device aboard the unmanned aerial vehicle at approximately thefirst time; determining a first plurality of pixel disparities betweenthe first image and the second image according to at least one of: anoptical flow algorithm; or a stereo matching algorithm; identifying atleast a first ground location that does not include at least one groundobstruction based at least in part on at least some of the firstplurality of pixel disparities; and causing a descent of the unmannedaerial vehicle toward the first ground location; capturing a third imageby the first imaging device at a second time, wherein the second timefollows the first time; capturing a fourth image by the second imagingdevice at approximately the second time; determining a second pluralityof pixel disparities between the third image and the fourth imageaccording to at least one of: the optical flow algorithm; or the stereomatching algorithm; identifying at least one airborne obstruction basedat least in part on at least some of the second plurality of pixeldisparities; and in response to identifying the at least one airborneobstruction, halting the descent of the unmanned aerial vehicle.
 19. Themethod of claim 18, wherein identifying at least the first groundlocation comprises: generating a first three-dimensional reconstructionbased at least in part on the at least some of the first plurality ofpixel disparities, wherein at least the first ground location isidentified based at least in part on the first three-dimensionalreconstruction, and wherein identifying the at least one airborneobstruction comprises: generating a second three-dimensionalreconstruction based at least in part on the at least some of the secondplurality of pixel disparities, wherein the at least one airborneobstruction is identified based at least in part on the secondthree-dimensional reconstruction.
 20. The method of claim 18, whereinidentifying at least the first ground location comprises: generating afirst difference image based at least in part on the at least some ofthe first plurality of pixel disparities, wherein at least the firstground location is identified based at least in part on the firstdifference image, and wherein identifying the at least one airborneobstruction comprises: generating a second difference image based atleast in part on the at least some of the second plurality of pixeldisparities, wherein the at least one airborne obstruction is identifiedwithin the second difference image.
 21. The method of claim 18, furthercomprising: causing a lateral variation in position of the unmannedaerial vehicle, wherein each of the first image and the second image iscaptured prior to causing the lateral variation, and wherein each of thethird image and the fourth image is captured following the lateralvariation.
 22. The method of claim 18, further comprising: capturing afifth image by the first imaging device at a third time, wherein thethird time follows the second time; capturing a sixth image by thesecond imaging device at approximately the third time; determining athird plurality of pixel disparities between the fifth image and thesixth image according to at least one of: the optical flow algorithm; orthe stereo matching algorithm; identifying at least a second groundlocation based at least in part on at least some of the third pluralityof pixel disparities, wherein an area between the unmanned aerialvehicle and the second ground location does not include the at least oneairborne obstruction; and causing a descent of the unmanned aerialvehicle toward the second ground location.
 23. The method of claim 18,wherein the at least one airborne obstruction comprises at least one ofa wire or a clothesline.